In known systems, a basic injection signal is formed in dependence on engine speed and load which, among others, is then also corrected in dependence on the battery voltage. The reason for this is that the pick-up time of injection depends to a substantial degree on the battery voltage. If the voltage were not corrected electronically, a delayed response of the injection valves ensuing therefrom would result in an insufficient duration of injection and thus an insufficient quantity of fuel injected. The lower the battery voltage, the less fuel would be supplied to the internal combustion engine. For this reason, a low battery voltage as it occurs, for example, during and after a cold start with the battery greatly discharged, has to be compensated for by a correspondingly selected extension of the base duration of injection in order for the internal combustion engine to receive the proper amount of fuel, the base duration of injection being dependent upon the speed and the load. In this connection, reference may be had to the publication "Bosch, Technische Unterrichtung, L-Jetronic", April 1981, pages 16 and 17.
In known systems, the voltage correction acts additively and is generated by means of a characteristic curve. This voltage correction is taken as a separate correction quantity.
However, in some operating ranges, this voltage correction does not perform optimally because of misadjustments at certain points.